Black males exhibit a steeper escalation in substance use (i.e., cross-over effects) and experience disproportionately higher rates of correlated poor health outcomes (e.g., HIV-related deaths and homicide) and low educational attainment compared with White males during emerging adulthood (ages 18 to 29 years). 1-3 Neighborhoods have been identified as important contexts for investigating substance use during emerging adulthood. 4 Yet, there is a fundamental gap in the current scientific evidence-base about the role of neighborhood conditions, beyond those defined by census data, in shaping substance use for Black emerging adult males. An equally notable evidence gap is created by the limited number of studies focusing on mechanisms that could explain why some Black emerging adult males exposed to less optimal neighborhood conditions engage in problematic (vs. non-problematic) substance use (i.e., alcohol and marijuana). This K01 application, entitled Neighborhoods, daily stress, affect regulation, & Black male substance use proposes integrated training and research to address these gaps by assessing potential pathways linking directly-observed neighborhood violence, alcohol, and drug activity to problematic substance use among Black male emerging adults. The potential pathways include theory-supported stress- affective mechanisms: daily stress, stress and androgenic hormones (as assessed through biomarkers), and affect regulation. The central hypothesis, grounded in Phenomenological Variant of Ecological Systems Theory5, and psychobiological models of stress, coping, and risk-taking,6-8 is that neighborhoods with high violence, alcohol, and drug activity instigate problematic substance use through increased daily stress experiences leading in turn to higher negative affect, and dysregulated cortisol and testosterone. Moreover, when these stress response processes occur in tandem with affect regulation strategies that encourage 'stuffing down' negative affect (i.e., emotion suppression), the effect on problematic substance use is expected to be heightened. The studies will employ a sample of non-substance dependent, Black emerging adult males (n = 66) drawn from Durham, NC neighborhoods (i.e., census block groups). A variety of assessment and analytic methods will be used including neighborhood social observations, Ecological Momentary Assessments (EMA), salivary hormone biomarker analyses, and focus groups. Three specific aims will be examined in two complementary studies: 1) to use the Neighborhood Inventory for Environmental Typology (NIfETy) 9, and Ecological Momentary Assessment (EMA) data to examine associations between neighborhood violence, alcohol, and drug activity (VAOD) and daily problematic alcohol and marijuana use; 2) to investigate daily stress-affective mechanisms linking neighborhood VAOD to daily problematic alcohol and marijuana use; and 3) to develop tailored messages for a future ecological momentary intervention designed to modulate stress-affective processes in real-time. Dr. Powell Hammond, who is trained in clinical psychology and health behavior and health education, and has focused her research career on using community-based approaches to investigate stress, gender, and health disparities, particularly among Black males. Training activities will include: formal didactics and hands-on instruction in conducting systemic social observations of neighborhoods, EMA, and salivary bioscience methods, workshops on tailored message development and ecological momentary intervention design, bioethics and responsible conduct in research training, and attendance at national and international conferences. She has assembled a strong interdisciplinary mentoring team that will guide her training and career development plans for building new skills in substance abuse research, neighborhood epidemiological assessment and social observational methods, ecological momentary assessment/intervention design, salivary biomarker measurement and data collection, and statistical methods for analyzing complex longitudinal models. The K01 award will increase her capabilities as an independent researcher to develop and test a fully powered ecological momentary intervention, as a separate R-level proposal. Results of the proposed research will also enhance current understanding of neighborhood effects on problematic substance use in Black males, inform development of ecologically valid addiction and relapse prevention interventions, and ultimately help to reduce substance use cross-over effects and substance abuse-related morbidity and mortality among Black emerging males.